1. Field of the Invention
The present invention relates to an optical lens, which is used for a component or the like of an optical instrument or information equipment, and a manufacturing method thereof and further concerns an optical device using the optical lens. Moreover, for example, the present invention relates to a lens, a lens manufacturing method, a lens manufacturing device, an optical device, an optical pickup device, an optical communication device, an optical sensor device, and a laser beam printer device.
2. Related Art of the Invention
In recent years, a lens has been widely used for a pickup of an optical communication disk, an optical communication module, a pickup of an optical disk device, a laser printer, a variety of optical sensors and so on as well as a camera and a telescope. These devices have been downsized with improved capability year after year, and even an optical lens of a several-millimeter or smaller has been realized (for example, a lens of 2-millimeter or smaller is available).
Further, at the time of assembling a variety of optical devices and components, a worker determines an installing direction of an optical lens according to a visual check on a curvature, a shape of the lens surface and so on, and the worker manually marks the surface before assembling and mounting.
Additionally, upon inspecting a lens, optical characteristics such as aberration, resolution, and transmittance are measured. However, as mentioned above, a lens has been recently reduced in size (for example, a lens of 2-millimeter or smaller is available), so that it has been increasingly difficult to inspect a lens to make final determination on the quality of the lens.
In many cases, a visual inspection for flaws and contamination has been conducted as a lens inspection. Such an inspection includes a visual check or image processing conducted on the entire surface of a lens.
However, in case of mounting a lens on a variety of optical devices, it has been more difficult to determine an installation surface of a lens because an optical lens is smaller with a fine shape, resulting in poor workability, and a step of marking for determination is additionally required, thereby increasing the manufacturing cost. Further, marking becomes more difficult as a lens is smaller.
The objective of the present invention is, in order to solve the above-mentioned problem, to provide an optical lens allowing a worker to readily determine an installation surface of the lens, a manufacturing method of the optical lens, and an optical device using the optical lens.
Further, in the case of a visual inspection by observation, the quality is determined by inspecting the entire surface of a lens. Thus, a lens having no problem about its capability is determined as a defective piece because of flaws or dust adhered to a region outside an effective area, even though the region is not fundamentally used. Particularly, due to returned products from a customer making such an incorrect determination, a yield may be reduced. Moreover, in a visual inspection by image processing, a lens surface is shiny, so that lighting and reflection from the surroundings make it difficult to determine the quality. Consequently, an image processing algorithm for determination may become complicated.
Furthermore, when accuracy of determination is increased, an inspecting step requires more time and work, thereby increasing a unit price of a lens.
As described above, it has not been possible to provide a high-quality lens with low manufacturing cost while maintaining a preferable yield.